1. Field of the Invention
This invention relates generally to a wetness sensing device for diapers and other undergarments to enable the prompt changing of the same when they become wet. In its particular aspects, the present invention relates to a reusable device containing a non-contacting capacitive sensor mounted on the external surface of any type of diaper and a transmitter for relaying the presence of a wetness condition to a remotely monitored station.
2. Description of the Prior Art
One of the primary causes of diaper rash is, of course, that diaper wearers frequently wet their diapers and, for one reason or another, remain in bodily contact with the wet diapers for prolonged periods before they are changed. While some diaper wearers may be able to communicate the presence of a wetness condition, a significant number of wearers, including infants and the aged, are not. Even then, by the time a communicative diaper wearer realizes the wetness, the effect of the wetness condition may have already caused or exacerbated a skin irritation.
The number of aged persons is increasing primarily due to improved health care. This has caused a corresponding increase in the number of bed-ridden patients, many of which wear disposable undergarments. For example, in care facilities, such as hospitals and nursing homes, it is estimated that approximately 30% of the patients are bed-ridden or otherwise incontinent and are thus required to wear diapers of some sort. For such patients, the timely changing of diapers is both an issue of comfort and hygiene.
It is desirable for a care provider to provide for both the comfort and hygiene of its patients. However, without the aid of electrical sensors, attendants in such a care facility must physically inspect for the presence of wetness in the diapers of their patients. This is often done according to a pre-determined schedule, regardless of the patient's urination schedule. Therefore, a patient who appears dry during a scheduled check may soon thereafter soil their diaper and be left to lie in the wet or soiled diaper until the next scheduled inspection. Also, checking on a predetermined schedule is both inefficient use of the attendants' time and leads to inconveniencing the patient more often than is necessary. Additionally, depending upon the amount of urination and how long since the discharge, the diaper may not appear to be wet to the attendant inspecting it, thus leaving the wearer in contact with a soiled garment.
Electrical alarm devices have previously been proposed as a means for informing an attendant that a wet diaper condition has occurred so that the diaper can be changed and the wearer's skin cleansed thus increasing comfort and reducing the likelihood of irritation. One example of such a proposed alarm device is disclosed in U.S. Pat. No. 3,460,123 issued to Bass. Bass shows a resistive-type of wet garment alarm system that employs a diaper formed with a pair of spaced conductive screens having an electrolyte disposed therebetween and a transmitter for producing a radio signal. The transmitter is electrically coupled to the screens and is adapted to produce a radio signal when the resistance between the screens falls below a predetermined level.
In use, the transmitter of Bass is secured to the upper waist portion of an infant's diaper, and the diaper is secured to its wearer with the pair of conductive screens positioned at the crotch portion of the diaper. When the diaper is wet by the wearer, urine flows into the crotch portion of the diaper and electrically bridges the space between the conductive screens thus reducing the resistance between the screens. This reduced resistance, in turn, actuates the transmitter to produce a radio signal for activating a remote alarm to alert a parent or attendant to the wet diaper condition.
Another system for detecting and signaling a wet diaper condition is disclosed in U.S. Pat. No. 4,106,001, issued to Mahoney, wherein a garment clip houses a resistive-type moisture detector and alarm. The garment clip is adapted to be clipped onto an exposed edge of a diaper or other garment to be monitored. An elongated strip of material is detachably connected at one end to the clip and is sized to be positioned in a region of the diaper subject to wetness such as, for example, the crotch region. The strip of material includes a pair of embedded spaced electrodes that are coupled to the detector/alarm. When urinated upon by the wearer of the undergarment, a partial electrical short circuit occurs between the electrodes at some point along the strip of material. This short circuit is detected by the moisture detector, which activates the alarm to provide an audible indication of urination by the infant or wearer.
Yet another wetness detector is disclosed in U.S. Pat. No. 4,754,264 issued to Okada et al. wherein a capacitive-type sensing unit is composed of a water permeable upper sheet, a water impermeable lower sheet, a pair of metal layers placed inside the diaper between the upper and lower sheets longitudinally through the crotch area, and an informing unit for powering the capacitor and processing the wetness detection signal. When the wearer urinates, wetness penetrates the permeable layer and affects the electrostatic capacitance of the capacitively-coupled metal layers in the diaper. The sensor is separated from the informing unit when the diaper is changed and is disposed of with the diaper.
A similar system is disclosed in U.S. Pat. No. 4,796,014 issued to Chia, wherein a safety pin with spaced electrical conductors is coupled to a resistive-type detector and alarm device attached to a diaper. When urine bridges the space between the electrical conductors of the safety pin, a detection circuit is completed, which, in turn, activates the alarm. The Chia device further includes a circuit to delay the sounding of the wetness alarm to ensure that it does not interfere with an infant's normal urination cycle.
Another wetness sensing device is disclosed in U.S. Pat. No. 5,469,145 issued to Johnson. Johnson shows a capacitive-type sensor with interleaved conductive plates of a sensing capacitor mounted on the outside of a housing which is then affixed to the external surface of the diaper being monitored. When the inside of the diaper becomes wet, the capacitance of the sensor changes and provides a signal to actuate a local alarm.
While these and similar devices have been somewhat successful in signaling a wet diaper condition, they still tend to exhibit numerous problems and shortcomings inherent in their respective designs. For instance, several of these devices include a pair of conductive electrodes built into the material forming the diaper itself. Such a configuration is shown in the patents of Bass and Okada et al. Obviously, manufacture of these types of diapers can be relatively expensive since special diaper forming machinery must be developed and implemented. Another common problem with prior art devices is that the detecting strips that reside in the diaper are configured as integral non-detachable elements of the detector and alarm circuits. With such a configuration, the entire device often must be discarded when the sensing strip becomes worn, which is inefficient and wasteful. Also, manufacturing the detection devices and alarms in some prior art devices can become complicated and costly. Finally, the mere fact that conductive electrodes must extend into the diaper to detect resistive or capacitive changes when the wearer wets is objectionable to many and, under the proper condition, may result in a mild shock to the wearer.
Of the capacitive types of detectors, the fact that the sensor may be located on the inside of the diaper is affected with the same problems as the intra-diaper resistive-type sensors. Requiring that the conductive plates of the capacitor to be disposed of with each diaper is also wasteful and expensive. Additionally, the device disclosed in Johnson teaches that the interleaved conductive plates of the sensing capacitor are mounted on the outside of a housing directly against the exterior surface of a diaper. Mounting of the sensor of the Johnson device directly against the surface of the diaper is necessary because of relatively high capacitance, i.e., low sensitivity, of the capacitive sensor design. This is undesirable since the plates may come into contact with the skin of the wearer thus triggering a false wetness condition. Additionally, the exposed capacitive plates are subject to becoming easily soiled since they are directly exposed.
Accordingly, there exists a continuing and heretofore unaddressed need for a sensitive wet diaper detector and alarm system that is usable with a conventional disposable or non-disposable diaper, is remotely monitorable, is inexpensive to produce, easy and convenient to use, does not necessarily require that conductive electrodes extend into the diaper itself, and that does not require expensive and bulky housings that must be secured to a wearer's garments. It is to the provision of such a wet diaper detector and monitoring system to which the present invention is primarily directed.